Thursday, February 26, 2009

Webster On China's `Silent' Bird Flu Infections

# 2833

Robert G. Webster is regarded as the father of influenza virology, having correctly posited more than 4 decades ago that human flu's are derived from bird flu's.

Webster holds the Rose Marie Thomas Chair in Virology at St. Jude Children's Research Hospital, and is also a fellow of the Royal Society of London, the Royal Society of Medicine and the Royal Society of New Zealand, and a member of the National Academy of Sciences of the United States.

Today Reuters has an interview with Dr. Webster regarding the recent human cases detected in China and Vietnam. Webster believes that asymptomatic ducks, harboring `silent infections', may be to blame.

A hat tip to newshound Kobie on the Flu Wiki for posting this article.

HONG KONG, Feb 26 (Reuters) - A leading virologist said on Thursday that ducks are to blame for the resurgence of the H5N1 bird flu virus in China and Vietnam, and called for wider surveillance and vaccination of ducks to stop the problem.

The virus has infected at least 14 people in both countries since the start of this year, killing seven of them.

Experts said what was mystifying about the latest round of outbreaks was the absence of the disease in poultry in China despite the human infections. H5N1 is passed primarily from animal to human.

Robert Webster, a leading H5N1 expert, told a medical conference in Hong Kong that 'silent infections' of H5N1 in ducks may be the reason behind the human cases in China.

Most types of ducks are not sickened by the virus and in most countries in Asia, they mingle freely with chickens, providing ample opportunity for the virus to jump between species.

'The problem is in the ducks in Asia, there is no visible disease in these birds,' said Webster of the St Jude Children's Research Hospital in the United States.

The absence of visible infection in poultry makes it harder to track the disease and take preventive measures.

'In China, there is no disease (in poultry) ... I suspect there are some viruses in duck populations that they (authorities) don't know about ... Maybe there are silent infections, it's a vast country.'

Webster said it was very difficult to get farmers to vaccinate their apparently healthy ducks, especially when these exercises cost a lot of money.

Waterfowl are known to be reservoirs of avian influenza viruses. The virus is largely asymptomatic in them, allowing the birds to migrate and spread the disease.

The idea that ducks may be behind the spread of the virus in S.E. Asia isn't new, of course. Having Dr. Webster voice his concerns, however, may induce some countries to work harder at controlling this viral reservoir.

As I said, when Webster speaks, people listen.

One final note, I'm somewhat perplexed by the numbers cited in this article stating that:

The virus has infected at least 14 people in both countries since the start of this year, killing seven of them.

As far as I know, China has only publicly confirmed 7 cases (although an 8th is strongly suspected) with 5 fatalities, and Vietnam has only confirmed 2 cases with 1 fatality.